Besides sporadic parathyroid adenomas, various hereditary types of hyperparathyroidism are caused by mutations of specific genes, including: multiple endocrine neoplasia type 1 and familial isolated hyperparathyroidism, caused by alterations in the MEN1 gene; familial hypercalcemia with hypercalciuria, attributable to CASR gene changes; and hyperparathyroidism-jaw tumor syndrome and familial isolated hyperparathyroidism, caused by HRP2 gene mutations [8,9,10]. Here, CASR is linked to familial isolated hyperparathyroidism.